Family of Planets

art by Laurie O'Keefe

Earth

Have you ever wanted to travel in space? In a way you already do, because you live on Earth, and Earth is a planet floating in space. There are other planets, too, a whole family of planets that scientists call our solar system.

The Sun

The word “solar” means “having to do with the Sun.” The planets in our solar system all circle the Sun in paths called orbits. Planets that are closer to the Sun have shorter orbits. It doesn't take them as long to travel around the Sun. Planets farther from the Sun have longer orbits. It takes Earth about 365 days—one year—to travel around the Sun.

Jupiter

The planets are alike in another important way. They all spin, or rotate. It takes Earth 24 hours, or one day, to spin around one time. As Earth spins, the parts that face the Sun are lit up—it is daytime there. The parts that face away from the Sun are dark—it is nighttime.

Neptune

If you could visit the other planets, you would find some strange and surprising worlds. Some are dry and rocky, while others are balls of swirling gases with solid centers. Some planets are much hotter than Earth—so hot that nothing can live there. That's because they are so close to the Sun. Other planets are far away from the Sun. They are very, very cold—colder than any place on Earth.

Venus

Earth is just the right distance from the Sun—it is not too hot and not too cold. Earth has water to drink and air to breathe. Earth is the only planet in our solar system where plants and animals and people can live.

The Solar System

Mercury

Mercury is the closest planet to the Sun. It has the shortest orbit of all—it goes around the Sun in only 88 days.Back to Top

Venus

Venus is a scorching, fiery planet with thousands of volcanoes. Venus's air is poisonous to humans. Its sky is orange and gloomy and pierced with flashes of lightning.Back to Top

Earth

From space, Earth looks blue and white and green—full of life and a wonderful planet to call home.Back to Top

Mars

Mars is a desert planet covered with rocks and a fine, red dust. There are no oceans or signs of life, but there is ice, and scientists believe there may be water under the ground. Sometimes violent winds blow huge dust storms across the whole planet, giving the sky a pinkish glow.Back to Top

Jupiter

Jupiter is the largest planet, much larger than Earth. But it is mainly a big ball of gas. Jupiter spins faster than any other planet. This swift spinning whips up huge, swirling windstorms. There is a giant red spot on Jupiter that scientists think may be a hurricane that has been blowing for hundreds of years.Back to Top

Saturn

Saturn's colorful rings may look solid, but they are really just floating pieces of ice and rock and space dust. Astronauts can't land on Saturn because it doesn't have a solid surface. It is made up mostly of thick clouds of gas.Back to Top

Uranus

Some planets spin faster than Earth, some slower. Uranus is the only planet that seems to spin on its side! Scientists think that Uranus may have been hit by a large object that tilted it millions of years ago.Back to Top

Neptune

Neptune is a cold blue planet far from the Sun. It's so cold that icy crystals, not hot lava, spew out of the volcanoes on one of its moons.Back to Top

Pluto

Pluto is the smallest planet—a ball of ice and rock that is smaller even than our Moon. It takes faraway Pluto 248 years to go around the Sun!Back to Top

And far beyond the planets are the stars!

Vocabulary

Activity

What is important about the distance between the Earth and the Sun?[anno: The distance between the Earth and Sun is just right. The Earth is close enough to be warm, but it is not so close that it is too hot.]

Why do you think it is so cold on Neptune?[anno: It is cold on Neptune because it is far away from the Sun.]

If you stood on Mercury, what do you think the Sun would look like? Why?[anno: The Sun would appear larger in the sky than it does from Earth because Mercury is closer to the Sun.]